Sa'id bin al-Musayyab (may Allah have mercy on him) narrates from Sayyiduna Mu'awiyah (may Allah be pleased with him): "That the Messenger of Allah (peace and blessings be upon him) forbade zur, and zur is that a woman joins (other) hair to her hair."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16774